917 research outputs found
The observed chemical structure of L1544
Prior to star formation, pre-stellar cores accumulate matter towards the
centre. As a consequence, their central density increases while the temperature
decreases. Understanding the evolution of the chemistry and physics in this
early phase is crucial to study the processes governing the formation of a
star. We aim at studying the chemical differentiation of a prototypical
pre-stellar core, L1544, by detailed molecular maps. In contrast with single
pointing observations, we performed a deep study on the dependencies of
chemistry on physical and external conditions. We present the emission maps of
39 different molecular transitions belonging to 22 different molecules in the
central 6.25 arcmin of L1544. We classified our sample in five families,
depending on the location of their emission peaks within the core. Furthermore,
to systematically study the correlations among different molecules, we have
performed the principal component analysis (PCA) on the integrated emission
maps. The PCA allows us to reduce the amount of variables in our dataset.
Finally, we compare the maps of the first three principal components with the
H column density map, and the T map of the core. The results of
our qualitative analysis is the classification of the molecules in our dataset
in the following groups: (i) the -CH family (carbon chain
molecules), (ii) the dust peak family (nitrogen-bearing species), (iii) the
methanol peak family (oxygen-bearing molecules), (iv) the HNCO peak family
(HNCO, propyne and its deuterated isotopologues). Only HCO and
CS do not belong to any of the above mentioned groups. The principal
component maps allow us to confirm the (anti-)correlations among different
families that were described in a first qualitative analysis, but also points
out the correlation that could not be inferred before.Comment: 29 pages, 19 figures, 2 appendices, accepted for publication in A&A,
arXiv abstract has been slightly modifie
Rotational spectroscopy of the HCCO and DCCO radicals in the millimeter and submillimeter range
The ketenyl radical, HCCO, has recently been detected in the ISM for the
first time. Further astronomical detections of HCCO will help us understand its
gas-grain chemistry, and subsequently revise the oxygen-bearing chemistry
towards dark clouds. Moreover, its deuterated counterpart, DCCO, has never been
observed in the ISM. HCCO and DCCO still lack a broad spectroscopic
investigation, although they exhibit a significant astrophysical relevance. In
this work we aim to measure the pure rotational spectra of the ground state of
HCCO and DCCO in the millimeter and submillimeter region, considerably
extending the frequency range covered by previous studies. The spectral
acquisition was performed using a frequency-modulation absorption spectrometer
between 170 and 650 GHz. The radicals were produced in a low-density plasma
generated from a select mixture of gaseous precursors. For each isotopologue we
were able to detect and assign more than 100 rotational lines. The new lines
have significantly enhanced the previous data set allowing the determination of
highly precise rotational and centrifugal distortion parameters. In our
analysis we have taken into account the interaction between the ground
electronic state and a low-lying excited state (Renner-Teller pair) which
enables the prediction and assignment of rotational transitions with up
to 4. The present set of spectroscopic parameters provides highly accurate,
millimeter and submillimeter rest-frequencies of HCCO and DCCO for future
astronomical observations. We also show that towards the pre-stellar core
L1544, ketenyl peaks in the region where - peaks,
suggesting that HCCO follows a predominant hydrocarbon chemistry, as already
proposed by recent gas-grain chemical models
Joint constraints on the lepton asymmetry of the Universe and neutrino mass from the Wilkinson Microwave Anisotropy Probe
We use the Wilkinson Microwave Anisotropy Probe (WMAP) data on the spectrum
of cosmic microwave background anisotropies to put constraints on the present
amount of lepton asymmetry L, parameterized by the dimensionless chemical
potential (also called degeneracy parameter) xi and on the effective number of
relativistic particle species. We assume a flat cosmological model with three
thermally distributed neutrino species having all the same mass and chemical
potential, plus an additional amount of effectively massless exotic particle
species. The extra energy density associated to these species is parameterized
through an effective number of additional species DeltaN_oth$. We find that
0<|xi|<1.1 and correspondingly 0<|L|<0.9 at 2sigma, so that WMAP data alone
cannot firmly rule out scenarios with a large lepton number; moreover, a small
preference for this kind of scenarios is actually found. We also discuss the
effect of the asymmetry on the estimation of other parameters and in particular
of the neutrino mass. In the case of perfect lepton symmetry, we obtain the
standard results. When the amount of asymmetry is left free, we find \sum m_nu
< 3.6 eV at 2sigma. Finally we study how the determination of |L| is affected
by the assumptions on DeltaN_oth. We find that lower values of the extra energy
density allow for larger values of the lepton asymmetry, effectively ruling
out, at 2sigma level, lepton symmetric models with DeltaN_oth=0.Comment: 11 pages, 2 figures. Uses RevTex4. Minor changes made to match
published versio
Abnormal Pain Sensation in Mice Lacking the Prokineticin Receptor PKR2: Interaction of PKR2 with Transient Receptor Potential TRPV1 and TRPA1
The amphibian Bv8 and the mammalian prokineticin 1 (PROK1) and 2 (PROK2) are new chemokine-like protein ligands acting on two G protein-coupled receptors, prokineticin receptor 1 (PKR1) and 2 (PKR2), participating to the mediation of diverse physiological and pathological processes. Prokineticins (PKs), specifically activating the prokineticin receptors (PKRs) located in several areas of the central and peripheral nervous system associated with pain, play a fundamental role in nociception. In this paper, to improve the understanding of the prokineticin system in the neurobiology of pain, we investigated the role of PKR2 in pain perception using pkr2 gene-deficient mice. We observed that, compared to wildtype, pkr2-null mice were more resistant to nociceptive sensitization to temperatures ranging from 46 to 48 \ub0C, to capsaicin and to protons, highlighting a positive interaction between PKR2 and the non-selective cation channels TRPV1. Moreover, PKR2 knock-out mice showed reduced nociceptive response to cold temperature (4 \ub0C) and to mustard oil-induced inflammatory hyperalgesia, suggesting a functional interaction between PKR2 and transient receptor potential ankyrin 1 ion (TRPA1) channels. This notion was supported by experiments in dorsal root ganglia (DRG) cultures from pkr1 and\u2013pkr2-null mice, demonstrating that the percentage of Bv8-responsive DRG neurons which were also responsive to mustard oil was much higher in PKR1 12/ 12 than in PKR2 12/ 12 mice. Taken together, these findings suggest a functional interaction between PKR2 and TRP channels in the development of hyperalgesia. Drugs able to directly or indirectly block these targets and/or their interactions may represent potential analgesics
Allergic bronchopulmonary aspergillosis in children with cystic fibrosis: An update on the newest diagnostic tools and therapeutic approaches
Cystic fibrosis (CF), the most common autosomal-recessive genetic disease in the Caucasian population, is characterized by frequent respiratory infections and progressive lung disease. Fungal species are commonly found in patients with CF, and among them, Aspergillus fumigatus is the most frequently isolated. While bacteria, particularly Pseudomonas aeruginosa, have a well-established negative effect on CF lung disease, the impact of fungal infections remains unclear. In patients with CF, inhalation of Aspergillus conidia can cause allergic bronchopulmonary aspergillosis (ABPA), a Th2-mediated lung disease that can contribute to disease progression. Clinical features, diagnostic criteria and treatment of ABPA are still a matter of debate. Given the consequences of a late ABPA diagnosis or the risk of ABPA overdiagnosis, it is imperative that the diagnostic criteria guidelines are reviewed and standardized. Along with traditional criteria, radiological features are emerging as tools for further classification as well as novel immunological tests. Corticosteroids, itraconazole and voriconazole continue to be the bedrock of ABPA therapy, but other molecules, such as posaconazole, vitamin D, recombinant INF-γ and Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) modulators, have been showing positive results. However, few studies have been conducted recruiting CF patients, and more research is needed to improve the prevention and the classification of clinical manifestations as well as to personalize treatment. Early recognition and early treatment of fungal infections may be fundamental to prevent progression of CF disease. The aim of this narrative review is to give an update on ABPA in children with CF
Distribution and kinematics of the HCN(3-2) emission down to the innermost region in the envelope of the O-rich star W Hya
We report high angular resolution observations of the HCN (3-2) line emission
in the circumstellar envelope of the O-rich star W Hya with the Submillimeter
Array. The proximity of this star allows us to image its molecular envelope
with a spatial resolution of just ~40 AU, corresponding to about 10 times the
stellar diameter. We resolve the HCN (3-2) emission and find that it is
centrally peaked and has a roughly spherically symmetrical distribution. This
shows that HCN is formed in the innermost region of the envelope (within ~10
stellar radii), which is consistent with predictions from pulsation-driven
shock chemistry models, and rules out the scenario in which HCN forms through
photochemical reactions in the outer envelope. Our model suggests that the
envelope decreases steeply in temperature and increases smoothly in velocity
with radius, inconsistent with the standard model for mass-loss driven by
radiative pressure on dust grains. We detect a velocity gradient of ~5 km/s in
the NW--SE direction over the central 40 AU. This velocity gradient is
reminescent of that seen in OH maser lines, and could be caused by the rotation
of the envelope or by a weak bipolar outflow.Comment: accepted for publication in ApJ
Coronavirus infections in children: From SARS and MERS to COVID-19, a narrative review of epidemiological and clinical features
Emerging and re-emerging viruses represent an important challenge for global public health. In the 1960s, coronaviruses (CoVs) were recognized as disease agents in humans. In only two decades, three strains of CoVs have crossed species barriers rapidly emerging as human pathogens resulting in life-threaten-ing disease with a pandemic potential: severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002, Middle-East respiratory syndrome coronavirus (MERS-CoV) in 2012 and the recently emerged SARS-CoV-2. This narrative review aims to provide a comprehensive overview of epidemiological, pathogenic and clinical features, along with diagnosis and treatment, of the ongoing epidemic of new coronavirus disease 2019 (COVID-19) in the pediatric population in comparison to the first two previous deadly coronavirus outbreaks, SARS and MERS. Literature analysis showed that SARS-CoV, MERS-CoV and SARS-CoV-2 infections seem to affect children less commonly and less severely as compared with adults. Since children are usually asymptomatic, they are often not tested, leading to an underestimate of the true numbers infected. Most of the documented infections belong to family clusters, so the importance of children in transmitting the virus remains uncertain. Like in SARS and MERS infection, there is the possibility that children are not an important reservoir for novel CoVs and this may have important implications for school attendance. While waiting for an effective against SARS-CoV-2, further prevalence studies in paediatric age are needed, in order to clarify the role of children in different age groups in the spread of the infection. (www.actabiomedica.it)
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